A method and apparatus for measuring the thickness of layers of fat and flesh in carcasses utilizing the difference in electrical conductivity between layers

ABSTRACT

A method and an apparatus for measuring the thickness of layers of fat and flesh in carcasses utilizing the difference in electrical conductivity between said layers. A probe with three surface electrodes is introduced in to the carcass said electrodes being connected to an AC bridge for connecting adjacent current paths formed in the layers between said electrodes thereto. The probe is moved on, until an unbalanced condition of the bridge is observed by indicator means. The linear distance between measuring points associated with the carcass surface and the probe, respectively, being, then, measured in order to obtain the thickness of the fat layer. The probe may be moved right through the carcass in order to determine total thickness thereof by detecting flesh to air transition and retracted again for repeating the measurement made during insertion. Alternatively, a probe provided with a plurality of surface electrodes may be inserted in a stationary position in the carcass, said electrodes being then connected successively to the bridge by switching means and recordings being taken of the switching steps where the bridge enters from a balanced to an unbalanced condition.

United States Patent Knudsen et al.

METHOD AND APPARATUS FOR MEASURING THE THICKNESS OF LAYERS 0F FAT ANDFLESH IN CARCASSES UTILIZING THE DIFFERENCE IN ELECTRICAL CONDUCTIVITYBETWEEN LAYERS lnventors: Erik Stenberg Knudsen, Roskilde; Svend ErikIversen, Ballerup; Svend Aage Lund,

Birkerod; Allan Northeved, Barsvaeerd, all of Denmark SlagteriernesForsknungsinstitut, Roskilde, Denmark Filed: Feb. 17, 1971 App]. No.:115,963

Assignee:

Foreign Application Priority Data Feb. 20, 1970 Denmark ..853

References Cited UNITED STATES PATENTS 9/1956 Whaley et al. ..324/65 X6/i96l Marsh et al. ..324/65 X l/l97l Johnston "73/304 PrimaryE.\'aminer--Stanley T. Krawczewicz Attorney-Kane, Dalsimer, Kane,Sullivan & Kurucz [5 7] ABSTRACT A method and an apparatus for measuringthe thickness of layers of fat and flesh in carcasses utilizing thedifference in electrical conductivity between said layers. A probe withthree surface electrodes is introduced in to the carcass said electrodesbeing connected to an AC bridge for connecting adjacent current pathsformed in the layers between said electrodes thereto. The probe is movedon, until an unbalanced condition of the bridge is observed by indicatormeans. The

linear distance between measuring points associated with the carcasssurface and the probe, respectively, being, then, measured in order toobtain the thickness of the fat layer. The probe may be moved rightthrough the carcass in order to determine total thickness thereof bydetecting flesh to air transition and retracted again for repeating themeasurement made during insertion. Alternatively, a probe provided witha plurality of surface electrodes may be inserted in a stationaryposition in the carcass, said electrodes being then connectedsuccessively to the bridge by switching means and recordings being takenof the switching steps where the bridge enters from a balanced to anunbalanced condition.

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ATTORNEY$ METHOD AND APPARATUS FOR MEASURING THE THICKNESS OF LAYERS OFFAT AND FLESH IN CARCASSES UTILIZING THE DIFFERENCE IN ELECTRICALCONDUCTIVITY BETWEEN LAYERS BACKGROUND OF THE INVENTION The presentinvention relates to a method for determining the thickness of layers offat and flesh in animal carcasses by means of electrical measuringbetween electrodes which are inserted, by means of a probe, into thecarcass, wherein the difference in conductivity in fat and flesh,respectively, is utilized and the linear distance between a measuringpoint associated with the surface of the carcass and a measuring pointon said probe is measured.

Methods for electrical measuring of the kind mentioned have been knownfor many years. However, these methods have appeared to be subject tosuch shortcomings that they did not gain ground in practice. Instead,another course has been followed, namely to construct devices by meansof which it is possible to perform an optical viewing of the interfacebetween fat and flesh.

SUMMARY OF THE INVENTION The present invention is based on therecognition of the fact that the variation which is found to exist fromcarcass to carcass in the resistance of the layer of fat and the layerof flesh, respectively, can give rise to difficulties in the measuringprocess. It is possible, however, to overcome these difficulties bymeans of a suitable method and an appropriate device.

According to the invention, a method for measuring the thickness oflayers of fat and flesh in carcasses is provided, comprising the stepsof connecting at least three longitudinally spaced, insulated surfaceelectrodes of a measuring probe to different junctions of an AC bridgecircuit comprising a source of an AC measuring current and indicatormeans,

adjusting said bridge circuit to a balanced condition,

introducing said measuring probe in the carcass to be measured from theouter surface of said fat layer in order to incorporate by means of saidthree electrodes adjacent current paths extending transversely relativeto said layers into two different branches of said bridge circuit,

observing the condition of said bridge circuit by said indicator meansduring continued movement of said probe into said carcass, and

measuring the penetration depth of one point of said probe at the momentwhen said bridge circuit enters from a balanced to an unbalancedcondition.

By these measures, such a degree of accuracy is attained in themeasuring results that it is possible to detect with certainty when theinterface between fat and flesh is reached when introducing the probeinto the object to be measured.

The use of an AC measuring current is found to be of substantialadvantage over the DC current previously used, inter alia, becauseuncontrollable contact potentials are avoided. The employment of abridge circuit makes it possible to measure differences in conductancebetween the fat and flesh layers, which prove to be approximatelyinvariant quantities in contradistinction to the absolute resistancevalues of the layers which differ from carcass to carcass. Furthermore,it becomes possible to use quite low measuring currents. Whereaspreviously electrodes were used which were located on the sloping frontface of a probe, it is suggested in the present invention to useelectrodes situated on the surface of the cylindrical part of the probe,which has been found to be an advantage in practice.

In the method according to the invention, an AC measuring current of arelatively high frequency is preferably used, said frequency being, forexample, of the order of magnitude of 40 kc/s.

in the method according to the invention, a measure is obtained of thelinear distance between the surface of the carcass and the interfacebetween the layers of fat and flesh.

In the method according to the invention, it is possible to move theprobe right through the measuring object and to perform readings orrecords of measuring results both when introducing and retracting theprobe. A storing and comparing of the results of the reading in the twocases can provide greater certainty in the thickness determination sincethe probability of coincidence of two erroneous indications, one duringthe introduction and one during the retraction, is low, and thedivergence in readings taken at the actual measuring point is relativelysmall.

A method according to the invention opens up the possibility of anautomation of this stage of the production process in a slaughter house,where manual processing is usually necessary due to the lack ofuniformity in the material that is to be measured and the necessity of aperson being present who is able to observe and record the measuringresults.

According to the invention such an automatical method for measuring thethickness of layers of fat and flesh in carcasses comprises the steps ofintroducing at least one measuring probe provided with a plurality oflongitudinally spaced, insulated surface electrodes into the carcass tobe measured from one outer surface thereof, until extreme electrodes onsaid probe are located at or beyond opposite outer surface of saidcarcass,

connecting by a stepwise electrical switching procedure said surfaceelectrodes in successive groups of three adjacent electrodes todifferent junctions of a balanced AC bridge circuit comprising a sourceof an AC measuring current and indicator means in order to incorporateby means of each of said groups adjacent current paths extendingtransversely relative to said layers into two different branches of saidbridge circuit,

observing by said indicator means the condition of said bridge circuitduring said switching procedure, and

recording the steps of said switching procedure, at which said bridgecircuit enters from a balanced into an unbalanced condition.

In such a method, it is possible by employing a number of separateprobes to carry out measuring operations at a corresponding number ofmeasuring points on the surface of the carcass simultaneously, so thatthe period of time for which the carcass has to remain at the measuringstation, is reduced.

The invention relates moreover, to a measuring apparatus comprising aprobe with measuring electrodes for use in determining the thickness oflayers of fat and flesh. Such a measuring apparatus is known, forexample, form U.S. Pat. No. 2,763,935.

In this prior art device, the measuring electrodes are fitted at thepoint of the probe.

According to the present invention, an apparatus is provided formeasuring the thickness of layers of fat and flesh in carcasses,comprising an AC bridge circuit with a source of an AC measuringcurrent, means connected to said bridge circuit for indicating balancedand unbalanced condition thereof, an elongated measuring probe with atleast three insulated measuring electrodes arranged on the surface of atubular part of said probe with a longitudinal spacing corresponding tothe desired measuring accuracy, said electrodes being adapted forcontacting said layers in contact points defining adjacent current pathsextending transversely relative to said layers, conductor meansextending inside said probe for connecting said electrodes to differentjunctions of said bridge circuit in order to incorporate said adjacentcurrent paths into two different branches thereof and means formeasuring the linear distance between a measuring point associated withthe surface of the carcass and a measuring point on the probe,respectively.

The measuring electrodes may be constructed in different ways independence on the purpose of the measuring. In a preferred embodiment ofthe measuring device according to the invention, the measuringelectrodes are annular.

In a measuring apparatus according to the invention the measuring probemay comprise a central core with a sharpedged spear member in one endthereof and a tubular envelope arranged coaxially with said core, saidconductor means extending in the spacing between said core and saidenvelope from said electrodes to the end of the probe remote from saidspear member.

Furthermore, according to the invention an apparatus may be provided formeasuring the thickness of layers of fat and flesh in carcassescomprising an AC bridge circuit with a source of an AC measuringcurrent, means connected to said bridge circuit for indicating balancedand unbalanced condition thereof, an elongated measuring probe with aplurality of insulated measuring electrodes arranged on the surface of atubular part thereof through a length corresponding to the maximum totalthickness of a carcass to be measured, said electrodes being adapted forcontacting said layers in contactpoints defining adjacent current pathsextending transversely relative to said layers, conductor meansextending inside said probe for connecting each of said electrodes to anelectrode terminal, and a switching device arranged between saidelectrode terminals and said bridge circuit for connecting successivelygroups of electrode tenninals associated with three adjacent electrodesto different junctions of said bridge circuit in order to incorporatethe adjacent current paths defined by said three electrodes into twodifferent branches of the bridge circuit.

In this apparatus it is, thus, possible to perform the measuring bysuccessive selection of the electrodes and the basis for a fullyautomatic measuring method is created, in which the measuring objects,by way of example, pigs carcasses, are automatically conveyed to ameasuring station where they are maintained in a predetermined position,whereupon a number of measuring probes corresponding to the desirednumber of measuring points are automatically introduced, the electrodesof said probes being then successively connected to the bridge circuitfor detecting and recording the thickness of the fat layer and,possibly, also that of the flesh layer, at each measuring point. Aftercompleted measuring, the probes are retracted and the measuring objectis moved on so as to make room for a new measuring object at themeasuring station.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention isexplained in greater detail with reference to the accompanyingschematical drawings, in which FIG. 1 shows an embodiment of a measuringapparatus according to the invention;

FIG. 2 shows a diagram to illustrate the employment of an AC bridgecircuit in the method according to the invention;

FIG. 3 shows an embodiment of a multi-electrode measuring apparatusaccording to the invention;

' FIG. 4 is a cross-sectional view of an embodiment of a measuring probefor use in the method according to the invention, and

FIG. 5 shows a block diagram to illustrate further details of theapparatus according to the invention.

DETAILED DESCRIPTION In FIG. 1, l designates a measuring probe providedwith a sharp-edged spear member in one end and secured in the oppositeend in a casing 2 incorporating indicator means in the form of a pointerinstrument 3. Said indicator means may also consist of two or threecontrol lamps having, preferably, different colors, e.g. red, yellow andgreen for indicating flesh, flesh-fat interface and fat, respectively.

The apparatus is provided with means for measuring the linear distancebetween a measuring point on the probe and a measuring point associatedwith the surface of the measuring object. In the example shown, amovable measuring device is provided in the form of a rule 4, which istelescopically slidable relative to a handle portion 5 which is securedto the housing of the pointer instrument 3. A finger rest or button 6 isrigidly connected to said rule and can be moved forwards and backwardsin a slot in the handle portion 5.

In the embodiment shown, the probe 1 has three annular electrodes 7, 8and 9, which are insulated relative to each other as well as to theprobe by means of four insulating rings 10, 11, 12 and 13. In theconstructional design of the probe, regard has to be taken to the factthat the rigidity of the probe should be sufficient for allowing theprobe to be introduced into the measuring objects without any risk ofdamaging it under the operating conditions prevailing in practice. InFIG. 4, a cross-sectional view of a preferred embodiment of a probe foruse in the measuring apparatus is shown.

In FIG. 4, 40 designates a narrow tubular envelope and 4] a cylindricalcore, both made of stainless steel or some other suitable material.Between the core and the envelope, spacing members of sector-shapedcross-section are interposed, which may, for example, be of insulatingmaterial. In the example shown, there are four such spacing members, ofwhich one is designated by 42. Between the spacing members, inside theprobe, longitudinal ducts 43 are formed for accomodating conductor lines44 to the electrodes 7, 8 and 9.

Alternatively, the probe may be constructed in another way. Theelectrodes and conductor lines may, for instance, be placed in milledrecesses in the surface of a solid, rod-shaped probe, the recesses beingfirst covered with a thin layer of insulating material, on to whichelectrically conductive material is applied, e.g. electrolytically or bymeans of sputtering, in order to form both electrodes and supply lines.The electrodes remain exposed, while the conductor lines are coveredwith insulating material.

In FIG. 1, the conductor lines inside the probe are, through a cable 14,connected to an electrical unit in the form of a separate casing 15incorporating a bridge circuit, a battery, an oscillator for generatingan AC measuring current and an amplifier for amplifying the signal fromthe bridge circuit, which is a measure of the difference in resistancebetween the two adjacent current paths formed between the electrodes 7,8 and 8, 9, respectively. The signal from the output of the amplifier isreturned through the cable 14 to the indicator 3 in the easing 2 of themeasuring device, the operator being, thus, able to read the result fromthe part of the measuring apparatus which is in his field of vision whenit is introduced into the measuring object.

When performing measuring operations, the operator first checks that theoperational condition of the device is in order, which is done by meansof a switch 16 on the unit 15, whereby the battery is connected to theindicator 3. Thereupon, the switch is put into its operational position,whereby the output of the amplifier is connected to the indicator 3. Theprobe is introduced into the measuring object. As long as the twocurrent paths 7, 8 and 8, 9 are both extending in the fat layer, theresistance in the branches 20 and 21 of the bridge circuit, in whichsaid current paths are connected, are relatively high, but uniform, videFIG. 2, in which the other two branches of the bridge circuit aredesignated by 22 and 23, said branches containing fixed resistors. An ACcurrent source or oscillator is designated by 24 and is connected in theone diagonal of the bridge circuit between the electrode 8 and thejunction between the resistors 22 and 23. The indicator 3 is connectedin the other diagonal of the bridge between the electrodes 7 and 9.

At the moment, at which the current path 7, 8 passes the interfacebetween the layers of fat and flesh, the balance of the bridge circuitis disturbed, which is observed by means of the indicator 3. Thepenetration of the probe into the measuring object is interrupted and itis now possible to read the thickness of the layer of fat on the rule 4by sliding one end thereof into abutment against the surface of themeasuring object by pressing the button 6 with a finger.

The electrode 8 constitutes the measuring point on the probe and theextension of said electrode in the axial direction of the probe is ameasure of the discrimination. The end face of the rule 4 which isintended to abut against the measuring object, determines anothermeasuring point, which is, thus, as sociated with the surface of themeasuring object, and it is the linear distance between the twomeasuring points that are being measured.

If the probe is moved right through the measuring object, the resistanceof the current paths becomes infinite. The same applies, of course,prior to the introduction of the probe into the measuring object. Thus,from the beginning to the end of the insertion of the probe into ameasuring object consisting of layers of fat and flesh, the following,clearly distinguishable states occur:

1. Infinitely high resistance in both current paths 7, 8 and 8,

2. Infinitely high resistance in the current path 8, 9 and fatresistance in the current path 7, 8;

3. Fat resistance in both current paths 7, 8 and 8, 9;

4. Flesh resistance in the current path 7, 8 and fat resistance in thecurrent path 8, 9;

5. Flesh resistance in both current paths;

6. Infinitely high resistance in the current path 7, 8 and fleshresistance in the current path 8, 9.

In the method described, a stepwise insertion of the probe takes placeand the attention of the operator has to be constantly paid to theindicator so that he is able to interrupt the insertion at the rightmoment and perform a reading by means of the above-mentioned slidablerule. He will possibly have to retract the probe slightly so that themeasuring point of the probe, the electrode 8, comes to be locatedcorrectly.

However, it is also possible to utilize a method in which a probe isinserted without performing any readings in the course of the insertion,whereupon the desired measurements are carried out with the stationaryprobe. This can be done electrically by means of a probe as shown inFIG. 3. This probe has a plurality of electrodes distributed evenly overa length of the probe corresponding at least to the maximum thickness ofthe measuring object. The electrodes are by means of conductor lines,connected to electrode terminals 33, 34, 35, 36 etc. associated with aswitch (not shown) which has three contract arms indicated schematicallywith arrows 30, 31 and 32. By successively connecting the contract armsto the electrode terminals and observing the measuring instrument, it ispossible to determine the thickness of the layers of fat and flesh onthe basis of the known linear spacing between the electrodes. It is thusnot necessary to perform any visual reading on a rule, but it ispossible to obtain the desired thickness values as multiples of thenumber of switching stages between positions, where an unbalancedcondition of the bridge circuit is detected, and the axial spacingbetween the electrodes. This axial spacing can be rendered arbitrarilysmall if the electrodes are not annular but are arranged, for instance,on the surface of the probe along a helical path and have suchcircumferential dimensions that the generatrices through a givenelectrode do not intersect the adjoining electrodes.

By means of such probe constructions, the possibility of a fullyautomatic method is opened up, in which measuring objects, e.g. pigscarcasses, are conveyed to a measuring station where they aresuccessively gripped and maintained in an anatomically defined position,subsequent to which a number of probes are simultaneously inserted intothe measuring object and the electrodes of each probe are successivelyconnected to the bridge circuit and the result is recorded, forinstance, on punched cards.

The switching procedure may take place by means of a separate switchingand bridge circuit for each probe or by means of a common circuit whichis successively connected to each of the probes.

FIG. 5 shows a block diagram of a measuring apparatus having circuitsfor electrical calibration and recording. The calibration takes placewhen the probe is moved into and right through the measuring object, inthat the electronic circuits are adapted to distinguish between signalsgenerated by fat-toflesh and flesh-to-air transitions, respectively. Therecording takes place when the probe is retracted, fat and flesh fat,respectively being marked, possibly via a digital voltmeter.

The marking may take place on a paper strip by means of a graphicrecorder or a punching device.

In FIG. 5, the probe, of which only two longitudinal sections are shown,is designated by 50. 51, 52 and 53 are three annular electrodes. The twocurrent paths to be incorporated in a bridge circuit (not shown), aresituated between the center electrode 52 and the two electrodes 51 and53. The center electrode 52 is connected to the output of an oscillator54 forming part of the bridge circuit. The two electrodes 51 and 53 areconnected to a unit 55 comprising two detectors, the output differencevoltage of which is supplied to a unit 56 comprising two peak detectors,one for positive and one for negative signal pulses, each of saiddetectors being connected. possibly through attenuating stages, to acomparator stage, the output voltages of which stages are, together, ledto a gate circuit 57 which is controlled by a trigger 58 which alsocontrols the peak detectors in the unit 56. The comparator stages supplyan output signal when the output signal from the unit 55 is numericallyhigher than the input signals to the comparator stages. The output ofthe gate circuit 57 is connected to a recording stage 59 with a view toreading. The output of the gate circuit 57 is, in addition, connected toa stage 60 comprising a trigger, a multivibrator, a trigger and amultivibrator, the output of which is connected to the trigger 58. Themultivibrators are of the one-shot type. The output pulses from stage 60serve to reset the detectors in the unit 55 and the trigger 58 whichmay, for example, be a Schmitt-trigger.

A transducer 61 is connected to the probe 50 which generates anelectrical signal which is a linear function of the depth of penetrationof the probe. The transducer may, for instance, be a potentiometer, themovable contact of which is rigidly connected to a spring-actuatedmember corresponding to the movable rule 4 shown in FIG. 1. The outputfrom the transducer 61 is connected, on the one hand, to the trigger 58and, on the other, to the recording stage 59.

The device described enables an automatic, purely electrical recordingof the measuring results without the operator having to do anything morethan to insert the probe into and move it right through the measuringobject and, thereupon, to retract it again. In the course of theinsertion, the circuits are set into an initial condition and themeasuring results are stored. During the retraction, the measuringresults are recorded subsequent to comparison with the results alreadystored. In the comparison, a maximum deviation of i 10 percent relativeto the stored results is allowed as a condition for recording.

By using a probe with a plurality of electrodes, like the one shown inFIG. 3, a similar electrical circuit can be used supplemented with aswitching circuit, the function of which is to connect successively theelectrodes of the stationary probe to the ridge circuit, first in onedirection and then in the opposite one, three adjacent electrodes beingconnected to the bridge circuit in each switching stage.

What we claim is:

1. A method for measuring the thickness of layers of fat and flesh incarcasses, comprising the steps of connecting at least threelongitudinally spaced, insulated surface electrodes of a measuring probeto different junctions of an AC bridge circuit comprising a source of anAC measuring current and indicator means, adjusting said bridge circuitto a balanced condition, introducing said measuring probe in the carcassto be measured from the outer surface of said fat layer in order toincorporate by means of said three electrodes adjacent current pathsextending transversely relative to said layers into two differentbranches of said bridge circuit,

observing the condition of said bridge circuit by said indicator meansduring continued movement of said probe into said carcass, and

measuring the penetration depth of one point of said probe at the momentwhen said bridge circuit enters from a balanced to an unbalancedcondition.

2. A method as claimed in claim 1, wherein an AC measuring current of arelatively high frequency is supplied to said bridge circuit from saidcurrent source.

3. A method as claimed in claim 2, wherein a frequency of the order ofmagnitude of 40 kc/s is used.

4. A method as claimed in claim 1, further comprising the steps ofmoving said probe further into said carcass subsequent to the measuringof said penetration depth, while observing the condition of said bridgecircuit, measuring the penetration depth of said one point of the probeat the moment when said bridge circuit enters again from a balanced intoan unbalanced condition,

retracting said probe from the latter penetration depth, while stillobserving the condition of said bridge circuit, and

measuring the penetration depth of said one point of the probe whenduring said retraction said bridge circuit enters again from a balancedto an unbalanced condition.

5. A method for measuring the thickness of layers of fat and flesh incarcasses, comprising the steps of introducing at least one measuringprobe provided with a plurality of longitudinally spaced, insulatedsurface electrodes into the carcass to be measured from one outersurface thereof, until extreme electrodes on said probe are located ator beyond opposite outer surface of said carcass,

connecting by a stepwise electrical switching procedure said surfaceelectrodes in successive groups of three adjacent electrodes todifferent junctions of a balanced AC bridge circuit comprising a sourceof an AC measuring current and indicator means in order to incorporateby means of each of said groups adjacent current paths extendingtransversely relative to said layers into two different branches of saidbridge circuit,

observing by said indicator means the condition of said bridge circuitduring said switching procedure, and

I recording the steps of said switching procedure, at which said bridgecircuit enters from a balanced into an unbalanced condition.

6. A method as claimed in claim 5, wherein an AC measuring current of arelatively high frequency is supplied to said bridge circuit from saidcurrent source.

7. A method as claimed in claim 6, wherein a frequency of the order ofmagnitude of 40 kc/s is used.

8. A method as claimed in claim 5, further comprising the steps ofsupporting the carcass to be measured at a measuring station in apreselected, anatomically defined position,

' introducing a number of measuring probes into said carcass at acorresponding number of measuring points on said outer surface,

carrying out said switching procedure through the surface electrodes ofeach probe, and

recording for each probe the steps of said switching procedure, at whichsaid bridge circuit enters from a balanced to an unbalanced condition.

9. A method as claimed in claim 8, wherein said probes are successivelyconnected to a common AC bridge circuit and said switching proceduresare carried out successively through the surface electrodes of allprobes.

10. A method as claimed in claim 8, further comprising the steps ofconveying a plurality of carcasses successively to said measuringstation, and

carrying out said switching procedures automatically.

1 1. An apparatus for measuring the thickness of layers of fat and fleshin carcasses, comprising an AC bridge circuit with a source of an ACmeasuring current, means connected to said bridge circuit for indicatingbalanced and unbalanced condition thereof, an elongated measuring probewith at least three insulated measuring electrodes arranged on thesurface of a tubular part of said probe with a longitudinal spacingcorresponding to the desired measuring accuracy, said electrodes beingadapted for contacting said layers in contact points defining adjacentcurrent paths extending transversely relative to said layers, conductormeans extending inside said probe for connecting said electrodes todifferent junctions of said bridge circuit in order to incorporate saidadjacent current paths into two different branches thereof and means formeasuring the linear distance between a measuring point associated withthe surface of the carcass and a measuring point on the probe,respectively.

12. An apparatus as claimed in claim 11, wherein said measuringelectrodes are annular.

13. An apparatus as claimed in claim 1 1, wherein said probe comprises acentral core with a sharp-edged spear member in one end thereof and atubular envelope arranged coaxially with said core, said conductor meansextending in the spacing between said core and said envelope from saidelectrodes to the end of the probe remote from said spear member.

14. An apparatus as claimed in claim 13, wherein amplifier means areconnected between said bridge circuit and said indicator means.

15. An apparatus as claimed in claim 14, comprising a handle secured tosaid remote end of said probe and incorporating said indicator means, aseparate casing incorporating said AC bridge circuit and said amplifiermeans and a flexible cable extending between said handle and saidseparate casing and incorporating conductor wires for connecting saidconductor means inside said probe to said different junctions of thebridge circuit and for connecting the output of said amplifier means tosaid indicator means.

16. An apparatus as claimed in claim 15, wherein said indicator meansconsist of three electrical control lamps of different colors, a firstone of said lamps serving to indicate that both of said current pathsextend in said fat layer, a second lamp serving to indicate that bothcurrent paths extend in said flesh layer and the third lamp serving toindicate that one current path extends in the fat layer, the other inthe flesh layer, i.e. that said current paths extend on each side of theinterface between said layers.

17. An apparatus as claimed in claim 15, wherein said indicator meansconsist of a pointer instrument having a measuring scale provided withmarks for fat and flesh, respectively.

18. An apparatus as claimed in claim 15, wherein said distance measuringmeans comprises a measuring scale slidable relative to the tubular partof said probe into and out of said handle and a fixed mark associatedwith said handle, said scale being calibrated so as to indicate in aposition, in which the free end thereof abuts against the surface of acarcass, the penetration depth of said measuring point on the proberelative to said measuring point associated with the surface of thecarcass.

19. An apparatus as claimed in claim 15, wherein means for automaticallyrecording the output signal from said amplifier means are connected withsaid casing, said distance measuring means comprising a transducerelement arranged on said probe and adapted for generating an electricalsignal for controlling said recording means in dependance on thepenetration depth of said measuring point on the probe relative to saidmeasuring point associated with the surface of said carcass.

20. An apparatus as claimed in claim 11, wherein the distances betweeneach pair of adjacent electrodes on said probe are equal to each other.

21. An apparatus for measuring the thickness of layers of fat and fleshin carcasses comprising an AC bridge circuit with a source of an ACmeasuring current, means connected to said bridge circuit for indicatingbalanced and unbalanced condition thereof, an elongated measuring probewith a plurality of insulated measuring electrodes arranged on thesurface of a tubular part thereof through a length corresponding to themaximum total thickness of a carcass to be measured, said electrodesbeing adapted for contacting said layers in contact points definingadjacent current paths extending transversely relative to said layers,conductor means extending inside said probe for connecting each of saidelectrodes to an electrode terminal, and a switching device arrangedbetween said electrode terminals and said bridge circuit for connectingsuccessively groups of electrode terminals associated with threeadjacent electrodes to different junctions of said bridge circuit inorder to incorporate the adjacent current paths defined by said threeelectrodes into two different branches of the bridge circuit.

22. An apparatus as claimed in claim 21, wherein said measuringelectrodes are arranged with uniform axial spacings along a helical pathon the surface of said tubular part of the

1. A method for measuring the thickness of layers of fat and flesh incarcasses, comprising the steps of connecting at least threelongitudinally spaced, insulated surface electrodes of a measuring probeto different junctions of an AC bridge circuit comprising a source of anAC measuring current and indicator means, adjusting said bridge circuitto a balanced condition, introducing said measuring probe in the carcassto be measured from the outer surface of said fat layer in order toincorporate by means of said three electrodes adjacent current pathsextending transversely relative to said layers into two differentbranches of said bridge circuit, observing the condition of said bridgecircuit by said indicator means during continued movement of said probeinto said carcass, and measuring the penetration depth of one point ofsaid probe at the moment when said bridge circuit enters from a balancedto an unbalanced condition.
 2. A method as claimed in claim 1, whereinan AC measuring current of a relatively high frequency is supplied tosaid bridge circuit from said current source.
 3. A method as claimed inclaim 2, wherein a frequency of the order of magnitude of 40 kc/s isused.
 4. A method as claimed in claim 1, further comprising the steps ofmoving said probe further into said carcass subsequent to the measuringof said penetration depth, while observing the condition of said bridgecircuit, measuring the penetration depth of said one point of the probeat the moment when said bridge circuit enters again from a balanced intoan unbalanced condition, retracting said probe from the latterpenetration depth, while still observing the condition of said bridgecircuit, and measuring the penetration depth of said one point of theprobe when during said retraction said bridge circuit enters again froma balanced to an unbalanced condition.
 5. A method for measuring thethickness of layers of fat and flesh in carcasses, comprising the stepsof introducing at least one measuring probe provided with a plurality oflongitudinally spaced, insulated surface electrodes into the carcass tobe measured from one outer surface thereof, until extreme electrodes onsaid probe are located at or beyond opposite outer surface of saidcarcass, connecting by a stepwise electrical switching procedure saidsurface electrodes in successive groups of three adjacent electrodes todifferent junctions of a balanced AC bridge circuit comprising a sourceof an AC measuring current and indicator means in order to incorpOrateby means of each of said groups adjacent current paths extendingtransversely relative to said layers into two different branches of saidbridge circuit, observing by said indicator means the condition of saidbridge circuit during said switching procedure, and recording the stepsof said switching procedure, at which said bridge circuit enters from abalanced into an unbalanced condition.
 6. A method as claimed in claim5, wherein an AC measuring current of a relatively high frequency issupplied to said bridge circuit from said current source.
 7. A method asclaimed in claim 6, wherein a frequency of the order of magnitude of 40kc/s is used.
 8. A method as claimed in claim 5, further comprising thesteps of supporting the carcass to be measured at a measuring station ina preselected, anatomically defined position, introducing a number ofmeasuring probes into said carcass at a corresponding number ofmeasuring points on said outer surface, carrying out said switchingprocedure through the surface electrodes of each probe, and recordingfor each probe the steps of said switching procedure, at which saidbridge circuit enters from a balanced to an unbalanced condition.
 9. Amethod as claimed in claim 8, wherein said probes are successivelyconnected to a common AC bridge circuit and said switching proceduresare carried out successively through the surface electrodes of allprobes.
 10. A method as claimed in claim 8, further comprising the stepsof conveying a plurality of carcasses successively to said measuringstation, and carrying out said switching procedures automatically. 11.An apparatus for measuring the thickness of layers of fat and flesh incarcasses, comprising an AC bridge circuit with a source of an ACmeasuring current, means connected to said bridge circuit for indicatingbalanced and unbalanced condition thereof, an elongated measuring probewith at least three insulated measuring electrodes arranged on thesurface of a tubular part of said probe with a longitudinal spacingcorresponding to the desired measuring accuracy, said electrodes beingadapted for contacting said layers in contact points defining adjacentcurrent paths extending transversely relative to said layers, conductormeans extending inside said probe for connecting said electrodes todifferent junctions of said bridge circuit in order to incorporate saidadjacent current paths into two different branches thereof and means formeasuring the linear distance between a measuring point associated withthe surface of the carcass and a measuring point on the probe,respectively.
 12. An apparatus as claimed in claim 11, wherein saidmeasuring electrodes are annular.
 13. An apparatus as claimed in claim11, wherein said probe comprises a central core with a sharp-edged spearmember in one end thereof and a tubular envelope arranged coaxially withsaid core, said conductor means extending in the spacing between saidcore and said envelope from said electrodes to the end of the proberemote from said spear member.
 14. An apparatus as claimed in claim 13,wherein amplifier means are connected between said bridge circuit andsaid indicator means.
 15. An apparatus as claimed in claim 14,comprising a handle secured to said remote end of said probe andincorporating said indicator means, a separate casing incorporating saidAC bridge circuit and said amplifier means and a flexible cableextending between said handle and said separate casing and incorporatingconductor wires for connecting said conductor means inside said probe tosaid different junctions of the bridge circuit and for connecting theoutput of said amplifier means to said indicator means.
 16. An apparatusas claimed in claim 15, wherein said indicator means consist of threeelectrical control lamps of different colors, a first one of said lampsserving to indicate that both of said current paths extend in said fatlayer, a second lamp serving to indicate that both current paths extendin said flesh layer and the third lamp serving to indicate that onecurrent path extends in the fat layer, the other in the flesh layer,i.e. that said current paths extend on each side of the interfacebetween said layers.
 17. An apparatus as claimed in claim 15, whereinsaid indicator means consist of a pointer instrument having a measuringscale provided with marks for fat and flesh, respectively.
 18. Anapparatus as claimed in claim 15, wherein said distance measuring meanscomprises a measuring scale slidable relative to the tubular part ofsaid probe into and out of said handle and a fixed mark associated withsaid handle, said scale being calibrated so as to indicate in aposition, in which the free end thereof abuts against the surface of acarcass, the penetration depth of said measuring point on the proberelative to said measuring point associated with the surface of thecarcass.
 19. An apparatus as claimed in claim 15, wherein means forautomatically recording the output signal from said amplifier means areconnected with said casing, said distance measuring means comprising atransducer element arranged on said probe and adapted for generating anelectrical signal for controlling said recording means in dependance onthe penetration depth of said measuring point on the probe relative tosaid measuring point associated with the surface of said carcass.
 20. Anapparatus as claimed in claim 11, wherein the distances between eachpair of adjacent electrodes on said probe are equal to each other. 21.An apparatus for measuring the thickness of layers of fat and flesh incarcasses comprising an AC bridge circuit with a source of an ACmeasuring current, means connected to said bridge circuit for indicatingbalanced and unbalanced condition thereof, an elongated measuring probewith a plurality of insulated measuring electrodes arranged on thesurface of a tubular part thereof through a length corresponding to themaximum total thickness of a carcass to be measured, said electrodesbeing adapted for contacting said layers in contact points definingadjacent current paths extending transversely relative to said layers,conductor means extending inside said probe for connecting each of saidelectrodes to an electrode terminal, and a switching device arrangedbetween said electrode terminals and said bridge circuit for connectingsuccessively groups of electrode terminals associated with threeadjacent electrodes to different junctions of said bridge circuit inorder to incorporate the adjacent current paths defined by said threeelectrodes into two different branches of the bridge circuit.
 22. Anapparatus as claimed in claim 21, wherein said measuring electrodes arearranged with uniform axial spacings along a helical path on the surfaceof said tubular part of the probe, the circumferential dimension of saidelectrodes being such that generatrices of said tubular partintersecting one electrode does not intersect the electrodes adjacentthereto.
 23. An apparatus as claimed in claim 21, wherein amplifiermeans are connected between said bridge circuit and said indicatormeans.
 24. An apparatus as claimed in claim 23, wherein said indicatormeans comprise means for automatically recording the output signal fromsaid amplifier means and means for controlling said recording means independance on the switching procedure carried out by said switchingdevice.